The present invention relates to block noise detecting apparatuses and block noise eliminating apparatuses, and more particularly to a block noise detecting apparatus and a block noise eliminating apparatus of a type eliminating block noise that arises in digital images as a result of image encoding carried out by compressing the digital images for transferring and recording.
Data compression is conventionally done for digital images, for example, to store the digital images with a lower volume of data. Such data compression includes a lossless encoding method and a lossy encoding method. In the lossless encoding method, encoded data, after decoding, can be completely identical to data before encoding. On the other hand, in the lossy encoding method, encoded data, after decoding, cannot always be identical to data before encoding and may include some degree of error.
The lossless encoding method generally includes discrete cosine transform (hereinafter, referred to as DCT). After DCT is carried out, quantization often follows. In this manner, when data is encoded first through DCT and then quantization, for example, the data cannot be completely identical to data before encoding and includes noise (error). This means that an encoding operation first through DCT and then quantization is lossy encoding.
To carry out DCT, first of all, a one-frame image is regionally divided into a plurality of blocks. A block herein is a group of 8xc3x978 two-dimensional pixel data, for example, and is regarded as a unit. Data encoded through DCT and quantization can be reconstituted by being subjected to inverse quantization and inverse DCT. Through the inverse quantization and inverse DCT, image data including block noise can be reconstituted.
Herein, block noise is described by referring to FIGS. 24(a)-(c).
FIGS. 24(a)-(c) are diagrams illustrating a conventional concept in eliminating the block noise. FIG. 24(a) shows a one-frame image 701, FIG. 24(b) is an enlarged view of a partial boundary (hereinafter, referred to as block boundary) 706 between a block 704 and a block 705 adjacent thereto in FIG. 24(a), and FIG. 24(c) shows a state of pixels in FIG. 24(b) after being smoothed.
It is now assumed, in FIG. 24(a), that pixels are in line in specific blocks in the one-frame image 701. In FIG. 24(b), when a pixel a in the block 704 and pixel b in the block 705 are presumably bordering on the block boundary 706, a difference in pixel level therebetween being larger than a difference in in-block pixel level between a pixel c and pixel d, for example, causes that part to be block noise. Accordingly, image quality in the part will be degraded to a greater degree.
As is known from this, block noise results from a level difference between pixels bordering on a block boundary in one-frame image.
The block noise is common in the lossy encoding method including DCT and quantization where processing is carried out on a block basis. To eliminate noise arisen in images, generally, the images are entirely subjected to smoothing. Smoothing is an operation of determining a pixel in average by using various pixels around a pixel to be processed. An operation of smoothing images with a low-pass filter (hereinafter, referred to as LPF) having a few taps is also referred to as smoothing. Such smoothing can eliminate not only block noise but noise, observed in images in their entirety as shown in FIG. 24(c).
Although there is no doubt that smoothing done on pixels can advantageously eliminate block noise, edges of images other than the block noise are also smoothed. Therefore, the images will disadvantageously be blurred.
Further, in the above conventional technique, the block noise can only be eliminated in a case where a block size and a block boundary are perfectly identified.
Still further, in a case where edges of images are bordering on the block boundary, the block noise causes less influence at the edges of the images. In the conventional technique in the foregoing, however, every block boundary is subjected to smoothing. In this manner, the edges of images bordering on the block boundary will be blurred, and thus, smoothing done on the block boundary may degrade image quality to a greater degree.
Therefore, an object of the present invention is to provide a block noise detecting apparatus of a type correctly detecting a block boundary targeted to eliminate block noise even when it is not clearly identified.
Another object of the present invention is to provide block noise eliminating apparatus of a type eliminating block noise without blurring images, not smoothing images even on a block boundary, if block noise thereon is low, and best matching to visual scenes.
Still another object of the present invention is to provide a block noise eliminating apparatus of a type eliminating block noise observed in an input signal even if the input signal is an analog signal or external digital signal (DVD or STB, for example) in a multi-format (interlace system or progressive system, for example).
Further, a dot clock can be regenerated in a video processing system by using the block noise detecting apparatus of the present invention.
The present invention has the following features to attain the objects above.
A first aspect is directed to a block noise detecting apparatus of a type detecting, from a digital video signal subjected to lossy encoding on a predetermined image block basis, block noise caused by decoding the video signal, the apparatus comprising:
means for detecting a level of the block noise in the video signal; and
means for detecting a block boundary (where the block noise is generated) in the video signal.
As described above, in the first aspect, by correctly detecting a block boundary of an image to be regionally divided into a plurality of blocks and a block noise level thereon, block noise can be detected.
A second aspect is directed to a block noise detecting apparatus of a type detecting, from a digital video signal subjected to lossy encoding on a predetermined image block basis, block noise caused by decoding the video signal, the apparatus comprising:
signal extracting means for receiving the video signal and extracting only a high frequency component therefrom;
absolute value taking means for taking an absolute value of a high frequency component signal outputted from the signal extracting means;
accumulating/adding means for accumulating/adding the absolute-value-taken high frequency component signal outputted from the absolute value taking means in a predetermined period;
periodicity detecting means for detecting periodicity of the block noise in accordance with an accumulation/addition result outputted from the accumulating/adding means; and
block boundary determining means for determining a block boundary (where the block noise is generated) from a periodic signal detected by the periodicity detecting means.
As described above, in the second aspect, by detecting periodicity of block noise and by correctly detecting a block boundary of an image to be regionally divided into a plurality of blocks, the block noise can be detected.
According to a preferable and concrete third aspect, in the second aspect, the block boundary determining means distinguishes, in binary, between positional information on the block boundary and positional information a remainder of the blocks. In this manner, a block boundary can be easily provided.
According to a fourth aspect, in the second and third aspects, the block noise detecting apparatus further comprises:
frame difference taking means for receiving the video signal and determining a signal difference among a plurality of predetermined frames thereof;
region determining means for determining, by referring to the signal difference outputted from the frame difference taking means for whether or not the difference is more than a predetermined threshold value, a region where the block noise to be eliminated is observed (hereinafter, referred to as noise region); and
block edge controlling means for masking the block boundary determined by the block boundary determining means in the noise region determined by the region determining means, and then determining a block boundary corresponding to the noise region.
As described above, in the fourth aspect, it becomes possible to further classify a block boundary compared to the second and third aspects by referring to the extent of image variation of images having block noise. As a result, only parts having high block noise observed in visual scenes can be detected as the block boundary.
According to a preferable and concrete fifth aspect, in the fourth aspect, the frame difference taking means determines a signal difference between a current frame and a one-frame-before frame. In this manner, only parts having high block noise observed in visual scenes can be detected as a block boundary.
According to a preferable and concrete sixth aspect, in the fourth and fifth aspects, the region determining means preferably distinguishes, in binary, between a part exceeding the threshold value and a part not exceeding the threshold value. In this manner, noise regions can be easily provided.
According to a seventh aspect, in the fourth to sixth aspects, the block noise detecting apparatus further comprises singular point eliminating means for excluding a noise part observed in a predetermined small region of the noise region determined by the region determining means, wherein
the block edge controlling means masks the block boundary determined by the block boundary determining means in the noise-part-excluded noise region outputted from the singular point eliminating means.
As described above, in the seventh aspect, the smaller regions in the image, in the fourth to sixth aspects, which hardly benefit from noise elimination by smoothing are eliminated. In this manner, processing of taking a frame difference can be enhanced and accordingly, image quality is improved and data is reduced in volume.
According to a preferable eighth aspect, in the second to seventh aspects, the signal extracting means, the absolute value taking means, the accumulating/adding means, and the periodicity detecting means each execute processing for the video signal in either a horizontal or vertical direction, or both directions.
According to a ninth aspect, in the eighth aspect,
when each of the processing is executed for the video signal in the vertical direction,
the periodicity detecting means successively changes frames used for detection according to a format of the video signal to be inputted.
As described above, in the ninth aspect, a block boundary can be correctly detected without deteriorating periodicity of block image regardless of formats (interlace system/progressive system, for example) of a video signal to be inputted in the eighth aspect.
A tenth aspect is directed to a block noise eliminating apparatus of a type detecting and eliminating, from a digital video signal subjected to lossy encoding on a predetermined image block basis, block noise caused by decoding the video signal, the apparatus comprising:
means for detecting a level of the block noise in the video signal;
means for detecting a block boundary (where the block noise is generated) in the video signal; and
means for eliminating, in the block boundary, only the block noise whose the detected level is more than a predetermined threshold value.
As described above, in the tenth aspect, by correctly detecting a block boundary of an image to be regionally divided into a plurality of blocks and a block noise level thereon, the block noise can be detected. In this manner, block noise observed on the block boundary can be eliminated.
An eleventh aspect is directed to a block noise eliminating apparatus of a type detecting and eliminating, from a digital video signal subjected to lossy encoding on a predetermined image block basis, block noise caused by decoding the video signal, the apparatus comprising:
signal extracting means for receiving the video signal and extracting only a high frequency component therefrom;
absolute value taking means for taking an absolute value of a high frequency component signal outputted from the signal extracting means;
accumulating/adding means for accumulating/adding the absolute-value-taken high frequency component signal outputted
from the absolute value taking means in a predetermined period;
periodicity detecting means for detecting periodicity of the block noise in accordance with an accumulation/addition result outputted from the accumulating/adding means;
block boundary determining means for determining a block boundary (where the block noise is generated) from a periodic signal detected by the periodicity detecting means; and
block noise eliminating means for eliminating the block noise with respect to the block boundary.
As described above, in the eleventh aspect, by detecting periodicity of block noise and by correctly detecting a block boundary of an image to be regionally divided into a plurality of blocks, the block noise can be detected. In this manner, block noise observed on the block boundary can be eliminated.
According to a preferable and concrete twelfth aspect, in the eleventh aspect, the block boundary determining means distinguishes, in binary, between positional information on the block boundary and positional information a remainder of the blocks. In this manner, a block boundary can be easily provided.
According to a thirteenth aspect, in the eleventh and twelfth aspects, the block noise eliminating apparatus further comprises:
frame difference taking means for receiving the video signal and determining a signal difference among a plurality of predetermined frames thereof;
region determining means for determining, by referring to the signal difference outputted from the frame difference taking means for whether or not the difference is more than a predetermined threshold value, a region where the block noise to be eliminated is observed (hereinafter, referred to as noise region); and
block edge controlling means for masking the block boundary determined by the block boundary determining means in the noise region determined by the region determining means, and then determining a block boundary corresponding to the noise region, wherein
the block noise eliminating means eliminates the block noise with respect to the block boundary corresponding to the noise region.
As described above, in the thirteenth aspect, it becomes possible to further classify a block boundary as compared to the eleventh and twelfth aspects by referring to the extent of image variation of images having block noise. As a result, only parts having high block noise observed in visual scenes can be detected and eliminated as the block boundary.
According to a preferable and concrete fourteenth aspect, in the thirteenth aspect, the frame difference taking means preferably determines a signal difference between a current frame and a one-frame-before frame. In this manner, only parts having high block noise observed in visual scenes can be detected and eliminated as the block boundary.
According to a preferable and concrete fifteenth aspect, in the thirteenth and fourteenth aspects, the region determining means distinguishes, in binary, between a part exceeding the threshold value and a part not exceeding the threshold value. In this manner, noise regions can be easily provided.
According to a sixteenth aspect, in the thirteenth to fifteenth aspects, the block noise eliminating means further comprises singular point eliminating means for excluding a noise part observed in a predetermined small region of the noise region determined by the region determining means, wherein
the block edge controlling means masks the block boundary determined by the block boundary determining means in the noise-part-excluded noise region outputted from the singular point eliminating means.
As described above, in the sixteenth aspect, the smaller regions in the image, in the thirteenth to fifteenth aspects, which hardly benefit from noise elimination by smoothing are eliminated. In this manner, processing of taking the frame difference can be enhanced and accordingly, image quality is improved and data is reduced in volume.
According to a preferable seventeenth aspect, in the eleventh to sixteenth aspects, the signal extracting means, the absolute value taking part, the accumulating/adding means, and the periodicity detecting means each preferably execute processing for the video signal in either a horizontal or vertical direction, or both directions.
According to an eighteenth aspect, in the seventeenth aspect, the block noise eliminating apparatus further comprises identifying means for identifying a format for the video signal to be inputted, wherein
when each of the processing is executed for the video signal in the vertical direction,
the identifying means has the periodicity determining means successively change frames used for detection according to the format.
As described above, in the eighteenth aspect, a block boundary can be correctly detected without deteriorating periodicity of block image regardless of formats (interlace system/progressive system, for example) of a video signal to be inputted in the seventeenth aspect.
A nineteenth aspect is directed to a block noise eliminating apparatus of a type detecting and eliminating, from a digital video signal subjected to lossy encoding on a predetermined image block basis, block noise caused by decoding the video signal, the apparatus comprising:
vertical block boundary detecting means for receiving the video signal and detecting, with respect to the video signal, a block boundary (where the block noise is generated) in the lateral direction and a block noise level on a screen;
horizontal block boundary detecting means for receiving the video signal and detecting, with respect to the video signal, the block boundary in a longitudinal direction and block noise level on the screen;
block area detecting means for specifying the block boundary in both longitudinal and lateral directions from detection results of the vertical block boundary detecting means and the horizontal block boundary detecting means; and
block boundary smoothing means for smoothing the video signal to be inputted in a predetermined manner corresponding to the block boundary in both the longitudinal and lateral directions specified by the block area detecting means.
As described above, in the nineteenth aspect, a block boundary and block noise level can be correctly detected. In this manner, smoothing can be properly done according to the block noise level, and thus, block noise can be eliminated more effectively for the best match to the visual scenes.
According to a twentieth aspect showing the preferable and concrete structure, in the nineteenth aspect, the vertical block boundary detecting means comprises:
a vertical high-pass filter (hereinafter, referred to as HPF) extracting only a vertical high frequency component of the video signal;
first absolute value taking means for taking an absolute value of a high frequency component signal outputted from the vertical HPF;
horizontal accumulating/adding means for accumulating/adding the absolute-value-taken high frequency component signal outputted from the first absolute value taking means in the horizontal direction;
a first HPF extracting high a frequency component from the accumulated/added high frequency component signal outputted from the horizontal accumulating/adding means;
first N-point accumulating/adding means for accumulating/adding a signal outputted from the first HPF on a predetermined N-point basis (where N is a positive integer);
a first temporal filter detecting the block noise level of the video signal by computing the signal outputted from the first HPF in the temporal direction;
first maximum value detecting means for determining a maximum value and a position thereof among N-piece accumulated/added values determined by the first N-point accumulating/adding means through accumulation/addition; and
first masking means for masking the block noise level detected by the first temporal filter at the position of the maximum value outputted from the first maximum value detecting means, and then determining a vertical block boundary corresponding to the position, wherein
the horizontal block boundary detecting means comprises:
a horizontal HPF extracting only a horizontal high frequency component of the video signal;
second absolute value taking means for taking an absolute value of a high frequency component signal outputted from the horizontal HPF;
vertical accumulating/adding means for accumulating/adding the absolute-value-taken high frequency component signal outputted from the second absolute value taking means in the vertical direction;
a second HPF extracting a high frequency component from the accumulated/added high frequency component signal outputted from the vertical accumulating/adding means;
N-point accumulating/adding means for accumulating/adding a signal outputted from the second HPF on a predetermined N-point basis;
a second temporal filter detecting the block noise level of the video signal by computing the signal outputted from the second HPF in the temporal direction;
second maximum value detecting means for determining a maximum value and a position thereof among the N-piece accumulated/added values determined by the second N-point accumulating/adding means through accumulation/addition; and
second masking means for masking the block noise level detected by the second temporal filter at the position of the maximum value outputted from the second maximum value detecting means and then determining a vertical block boundary corresponding to the position.
In this manner, it becomes possible to detect the block noise level with less variation in the temporal direction, and to execute smoothing in an appropriate manner according to the block noise level. Accordingly, block noise can be eliminated more effectively for the best match to the visual scenes.
A twenty-first aspect is directed to a block noise eliminating apparatus of a type detecting and eliminating, from a digital video signal subjected to lossy encoding on a predetermined image block basis, block noise caused by decoding the video signal, the apparatus comprising:
AD converting means for receiving the video signal in an analog fashion and then converting the same into a digital fashion;
digital decoding means for receiving the video signal in an encoded digital fashion for decoding and outputting the decoded block boundary information;
a selector receiving the video signal outputted from the AD converting means and the video signal outputted from the digital decoding means and selectively outputting either one of the video signals as is externally instructed;
vertical block boundary detecting means for receiving the video signal selected by the selector and detecting, with respect to the video signal, a block boundary (where the block noise is generated) in the lateral direction and a block noise level on a screen;
horizontal block boundary detecting means for receiving the video signal selected by the selector and detecting, with respect to the video signal, the block boundary in the longitudinal direction and the block noise level on a screen;
block area detecting means for specifying the block boundary in both longitudinal and lateral directions from detection results of the vertical block boundary detecting means and the horizontal block boundary detecting means; and
block boundary smoothing means for smoothing the video signal to be inputted in a predetermined manner corresponding to the block boundary in both longitudinal and lateral directions specified by the block area detecting means, wherein
the vertical block boundary detecting means and the horizontal block boundary detecting means output, to the block area detecting means, the block boundary based on each of the detection results when the selector selects the video signal outputted from the AD converting means, and output the block boundary based on the block boundary information outputted from the digital decoding means when the selector selects the video signal outputted from the digital decoding means.
As described above, in the twenty-first aspect, a block boundary and block noise level corresponding to a video signal to be inputted can be correctly detected. In this manner, smoothing can be done in a proper manner according to the block noise level, and thus block noise can be eliminated more effectively for the best match to the various visual scenes to be inputted.
According to a twenty-second aspect showing the preferable and concrete structure, in the twenty-first aspect,
the vertical block boundary detecting means preferably comprises:
a vertical high-pass filter (hereinafter, referred to as HPF) extracting only a vertical high frequency component of the video signal;
first absolute value taking means for taking an absolute value of a high frequency component signal outputted from the vertical HPF;
horizontal accumulating/adding means for accumulating/adding the absolute-value-taken high frequency component signal outputted from the first absolute value taking means in the horizontal direction;
a first HPF extracting a high frequency component from the accumulated/added high frequency component signal outputted from the horizontal accumulating/adding means;
first N-point accumulating/adding means for accumulating/adding a signal outputted from the first HPF on a predetermined N-point basis (where N is a positive integer);
a first temporal filter detecting the block noise level of the video signal by computing the signal outputted from the first HPF in the temporal direction;
first maximum value detecting means for determining a maximum value and a position thereof among N-piece accumulated/added values determined by the first N-point accumulating/adding means through accumulation/addition;
a first selector synchronizing with the selector""s selection and selectively outputting either one of the block boundary information outputted from the digital decoding means or the position of the maximum value outputted from the first maximum value detecting means; and
first masking means for masking the block noise level detected by the first temporal filter at the block boundary outputted from the first selector, and determining a vertical block boundary corresponding to the position, wherein
the horizontal block boundary detecting means comprises:
a horizontal HPF extracting only a horizontal high frequency component of the video signal;
second absolute value taking means for taking an absolute value of a high frequency component signal outputted from the horizontal HPF;
vertical accumulating/adding means for accumulating/adding the absolute-value-taken high frequency component signal outputted from the second absolute value taking means in the vertical direction;
a second HPF extracting a high frequency component from an accumulated/added high frequency component signal outputted from the vertical accumulating/adding means;
N-point accumulating/adding means for accumulating/adding a signal outputted from the second HPF on a predetermined N-point basis;
a second temporal filter detecting the block noise level of the video signal by computing the signal outputted from the second HPF in the temporal direction;
second maximum value detecting means for determining a maximum value and a position thereof among the N-piece
accumulated/added values determined by the second N-point accumulating/adding means through accumulation/addition;
a second selector synchronizing with the selector""s selection and selectively outputting either one of the block boundary information outputted from the digital decoding means or the position of the maximum value outputted from the second maximum value detecting means; and
second masking means for masking the block noise level detected by the second temporal filter at the block boundary outputted from the second selector, and determining a vertical block boundary corresponding to the position.
In this manner, it becomes possible to detect the block noise level less in variation in the temporal direction, and to execute smoothing in an appropriate manner according to the block noise level. Accordingly, block noise can be eliminated more effectively for the best match to the various visual scenes to be inputted.
According to a twenty-third aspect showing the preferable and concrete structure, in the twentieth and twenty-second aspects,
the block boundary smoothing means preferably comprises:
a horizontal HPF extracting only a horizontal high frequency component of the video signal;
first multiplying means for multiplying an output of the horizontal HPF and an output of the horizontal block boundary detecting means;
first deducting means for deducting an output of the first multiplying means from the video signal;
a vertical HPF extracting only a vertical high frequency component of the video signal;
second multiplying means for multiplying an output of the vertical HPF and an output of the vertical block boundary detecting means; and
second deducting means for deducting an output of the second multiplying means from the video signal, wherein
the block noise is eliminated according to the block noise level.
In this manner, block noise can be effectively eliminated without deteriorating a video signal to be inputted.
According to a twenty-fourth aspect, in the nineteenth to twenty-third aspects, the block noise eliminating apparatus further comprises picture enhancing means for controlling a picture enhancement level emphasizing an outline part of the video signal according to the block noise level detected by the horizontal block boundary detecting means and the vertical block boundary detecting means.
As described above, in the twenty-fourth aspect, it becomes possible to properly carry out picture enhancement according to the block noise level, whereby picture enhancement of a video signal can be done without emphasizing block noise in the nineteenth to twenty-third aspects.
According to a twenty-fifth aspect, in the nineteenth to twenty-fourth aspects, the block noise eliminating apparatus further comprises controlling means for specifying the video signal (type or quality thereof, for example) to be inputted in accordance with the block noise level detected by the horizontal block boundary detecting means and the vertical block boundary detecting means, and
the controlling means on-screen-displays a result of the specification on a screen in a predetermined format.
As described above, in the twenty-fifth aspect, effects obtained by elimination of video sources or block noise can be acknowledged at a glance by on-screen-displaying information in the nineteenth to twenty-fourth aspects.
A twenty-sixth aspect is directed to a vertical block boundary detecting apparatus of a type detecting, from a digital video signal subjected to lossy encoding on a predetermined image block basis, block noise in the vertical direction caused by decoding the video signal, the apparatus comprising:
a vertical high-pass filter (hereinafter, referred to as HPF) receiving the video signal and extracting only a vertical high frequency component of the video signal;
absolute value taking means for taking an absolute value of a high frequency component signal outputted from the vertical HPF;
horizontal accumulating/adding means for accumulating/adding the absolute-value-taken high frequency component signal outputted from the absolute value taking means in the horizontal direction;
an HPF extracting a high frequency component from the accumulated/added high frequency component signal outputted from the horizontal accumulating/adding means;
N-point accumulating/adding means for accumulating/adding a signal outputted from the HPF on a predetermined N-point basis (where N is a positive integer);
a temporal filter detecting the block noise level of the video signal by computing the signal outputted from the HPF in the temporal direction;
maximum value detecting means for determining a maximum value and a position thereof among N-piece accumulated/added values determined by the N-point accumulating/adding means through accumulation/addition; and
masking means for masking the block noise level detected by the temporal filter at the position of the maximum value outputted from the maximum value detecting means, and determining a vertical block boundary corresponding to the position.
As described above, in the twenty-sixth aspect, a device for detecting a block boundary in the vertical direction is structured separately.
A twenty-seventh aspect is directed to a horizontal block boundary detecting apparatus of a type detecting, from a digital video signal subjected to lossy encoding on a predetermined image block basis, block noise in the horizontal direction caused by decoding the video signal, the apparatus comprising:
a horizontal high-pass filter (hereinafter, referred to as HPF) receiving the video signal and extracting only a vertical high frequency component of the video signal;
absolute value taking means for taking an absolute value of a high frequency component signal outputted from the horizontal HPF;
vertical accumulating/adding means for accumulating/adding the absolute-value-taken high frequency component signal outputted from the absolute value taking means in the vertical direction;
an HPF extracting a high frequency component from the accumulated/added high frequency component signal outputted from the vertical accumulating/adding means;
N-point accumulating/adding means for accumulating/adding a signal outputted from the HPF on a predetermined N-point basis (where N is a positive integer);
a temporal filter detecting the block noise level of the video signal by computing the signal outputted from the HPF in the temporal direction;
maximum value detecting means for determining a maximum value and a position thereof among N-piece accumulated/added values determined by the N-point accumulating/adding means through accumulation/addition; and
masking means for masking the block noise level detected by the temporal filter at the position of the maximum value outputted from the maximum value detecting means, and determining a horizontal block boundary corresponding to the position.
As described above, in the twenty-seventh aspect, a device for detecting a block boundary in the horizontal direction is structured separately.
A twenty-eighth aspect is directed to a dot clock controlling apparatus of a type controlling a dot clock to be regenerated in a video processing system in which a digital video signal subjected to lossy encoding on a predetermined image block basis is processed, the apparatus comprising:
clock generating means for generating the dot clock used in the video processing system in accordance with a horizontal synchronizing pulse;
horizontal block boundary detecting means for receiving the video signal and detecting a longitudinal block boundary (where block noise is generated) on a screen with respect to the video signal; and
controlling means for changing delay of the clock generating means in such a manner that the block boundary detected by the horizontal block boundary detecting means periodically has a single maximum point (peak).
As described above, in the twenty-eighth aspect, a horizontal block boundary corresponding to the video signal to be inputted is detected, and then a dot clock is regenerated according to positions thereof. In this manner, a clock whose phase is coincided with that of a dot clock of the video signal can be correctly regenerated.
According to a twenty-ninth aspect showing the preferable and concrete structure, in the twenty-eighth aspect, the horizontal block boundary detecting means comprises:
a horizontal high-pass filter (hereinafter, referred to as HPF) receiving the video signal and extracting only a vertical high frequency component of the video signal;
absolute value taking means for taking an absolute value of a high frequency component signal outputted from the horizontal HPF;
vertical accumulating/adding means for accumulating/adding the absolute-value-taken high frequency component signal outputted from the absolute value taking means in the vertical direction;
an HPF extracting a high frequency component from the accumulated/added high frequency component signal outputted from the vertical accumulating/adding means; and
N-point accumulating/adding means for accumulating/adding a signal outputted from the HPF on a predetermined N-point basis (where N is a positive integer).
In this manner, it becomes possible to correctly regenerate a clock whose phase is coincided with that of a dot clock of the video signal.
A thirtieth aspect is directed to a recording medium containing a program recorded thereon, to be run in a computer device, for detecting block noise from a digital video signal subjected to lossy encoding on a predetermined image block basis caused by decoding the video signal, the program for realizing an operational environment on the computer device comprising the steps of:
extracting only a high frequency component from the video signal;
taking an absolute value of the extracted high frequency component signal;
accumulating/adding the absolute-value-taken high frequency component signal in a predetermined period;
detecting periodicity of the block noise in accordance with the accumulation/addition result; and
determining a block boundary (where the block noise is generated) in accordance with a signal having the detected periodicity.
According to a thirty-first aspect, in the thirtieth aspect, the program further comprises a step of eliminating the block noise with respect to the block boundary.
According to a preferable and concrete thirty-second aspect, in the thirtieth and thirty-first aspects, in the step of determining the block boundary, positional information on the block boundary and positional information on the rest are distinguished, in binary, from each other.
According to a thirty-third aspect, in the thirtieth to thirty-second aspects, the program further comprises the steps of:
determining a signal difference among a plurality of predetermined frames of the video signal;
determining a region where block noise to be eliminated is observed (hereinafter, referred to as noise region) with reference whether or not the signal difference is larger than a predetermined threshold value; and
masking the block boundary in the noise region, and determining a block boundary corresponding to the noise region.
According to a preferable and concrete thirty-fourth aspect, in the thirty-third aspect, in the step of determining the signal difference, a signal difference between a current frame and a one-before-frame is determined.
According to a preferable and concrete thirty-fifth aspect, in the thirty-third to thirty-fourth aspects, in the step of determining the noise region, a part exceeding the threshold value and a part not exceeding the threshold value are distinguished, in binary, from each other.
According to a thirty-sixth aspect, in the thirty-third to thirty-fifth aspects, the recording medium further comprises a step of eliminating a noise part in a predetermined small region of the noise region, wherein
in the step of determining a block boundary corresponding to the noise block, the block boundary is masked in the noise-part-eliminated noise region.
According to a preferable and concrete thirty-seventh aspect, in the thirtieth to thirty-sixth aspects, each of the steps is executed in either a horizontal direction or vertical direction of the video signal, or in both directions.
According to a thirty-eighth aspect, in the thirty-seventh aspect, when each of the processing is executed in the vertical direction of the video signal, in the step of detecting periodicity, frames used for detection are successively changed corresponding to a format of the video signal to be inputted.
A thirty-ninth aspect is directed to a recording medium containing a program recorded thereon, to be run in a computer device, for detecting block noise from a digital video signal subjected to lossy encoding on a predetermined image block basis caused by decoding the video signal, the program for realizing an operational environment on the computer device comprising the steps of:
detecting, with respect to the video signal, a block boundary (where the block boundary is generated) in the lateral direction and a block noise level on the screen;
detecting, with respect to the video signal, the block boundary in the longitudinal direction and block noise level on the screen;
specifying the block boundary in both longitudinal and lateral directions from a detection result obtained in the step of detecting as to the lateral direction and the step of detecting as to the longitudinal direction; and
smoothing the video signal in a predetermined manner corresponding to the block boundary in both the longitudinal and lateral directions.
According to a fortieth aspect showing the preferable and concrete technique, in the thirty-ninth aspect,
the step of detecting as to the lateral direction comprises the steps of:
extracting only a vertical high frequency component from the video signal;
taking an absolute value of the extracted high frequency component signal;
accumulating/adding the absolute-value-taken high frequency component signal in the horizontal direction;
again extracting a high frequency component from the accumulated/added high frequency component signal;
accumulating/adding a signal outputted in the step of again extracting the high frequency component on a predetermined N-point basis (N is a positive integer);
detecting the block noise level of the video signal by computing the signal outputted in the step of again extracting high frequency component in the temporal direction; determining a maximum value and a position thereof among N-piece accumulated/added values determined by the accumulation/addition; and
masking the detected block noise level at the position of the maximum value, and determining a vertical block boundary corresponding to the position, and
the step of detecting as to the longitudinal direction comprises the steps of:
extracting only a horizontal high frequency component of the video signal;
taking an absolute value of the extracted high 10 frequency component signal;
accumulating/adding the absolute-value-taken high frequency component signal in the vertical direction;
again extracting a high frequency component from the accumulated/added high frequency component signal;
accumulating/adding a signal outputted in the step of again extracting the high frequency component on a predetermined N-point basis;
detecting the block noise level of the video signal by computing the signal outputted in the step of again extracting high frequency component in the temporal direction;
determining a maximum value and a position thereof among the N-piece accumulated/added values determined by the accumulation/addition; and
masking the detected block noise level at the position of the maximum value, and determining a vertical block boundary corresponding to the position.
A forty-first aspect is directed to a recording medium containing a program recorded thereon, to be run in a computer device, for detecting block noise from a digital video signal subjected to lossy encoding on a predetermined image block basis caused by decoding the video signal, the program for realizing an operational environment on the computer device further comprising the steps of:
converting the video signal in an analog fashion into a digital fashion;
decoding the digital-encoded video signal;
outputting the decoded block boundary information;
selecting either one of a video signal outputted in the converting step or a video signal outputted in the decoding step as is externally instructed;
detecting a lateral block boundary on a screen and a block noise level with respect to the video signal outputted in the selecting step;
detecting a longitudinal block boundary on a screen and a block noise level with respect to the video signal outputted in the selecting step;
specifying the block boundary in both longitudinal and lateral directions from detection results obtained in the step of detecting the lateral direction and the step of detecting the longitudinal direction; and
smoothing the video signal in a predetermined manner according to the block boundary in both the longitudinal and lateral directions, wherein
in the step of detecting as to lateral direction and the step of detecting as to longitudinal direction, the block boundary based on each of the detection results is outputted for the video signal outputted in the converting step, and the block boundary based on the decoded block boundary information are outputted for the video signal outputted in the decoding step.
According to a forty-second aspect showing the preferable and concretive technique, in the forty-first aspect, the step of detecting as to the lateral direction comprises the steps of:
extracting only a vertical high frequency component of the video signal;
taking an absolute value of the extracted high frequency component signal;
accumulating/adding the absolute-value-taken high frequency component signal in the horizontal direction-;
again extracting high frequency component from the accumulated/added high frequency component signal;
accumulating/adding a signal outputted in the step of again extracting the high frequency component on a predetermined N-point basis (n is a positive integer);
detecting the block noise level of the video signal by computing the signal outputted in the step of again extracting high frequency component in the temporal direction;
determining a maximum value and a position thereof among N-piece accumulated/added values determined by the accumulation/addition; and
synchronizing with the selecting step, and selectively outputting either one of the block boundary information and the maximum value position; and
masking the block noise level at the block boundary outputted in the selectively outputting step, and determining a vertical block boundary corresponding to the position, and
the step of detecting as to longitudinal direction comprises the steps of:
extracting only a horizontal high frequency component of the video signal;
taking an absolute value of the extracted high frequency component signal;
accumulating/adding the absolute-value-taken high frequency component signal in the vertical direction-;
again extracting a high frequency component from the accumulated/added high frequency component signal;
accumulating/adding a signal outputted in the step of again extracting the high frequency component on a predetermined N-point basis;
detecting the block noise level of the video signal by computing the signal outputted in the step of again extracting the high frequency component in the temporal direction;
determining a maximum value and a position thereof among the N-piece accumulated/added values determined by the accumulation/addition; and
synchronizing with the selecting step, and selectively outputting either one of the block boundary information or the position of the maximum value; and
masking the block noise level at the block boundary outputted in the selectively outputting step, and determining a horizontal block boundary corresponding to the position.
According to a forty-third aspect, in the fortieth and forty-second aspects,
the smoothing step further comprises:
a horizontal step of extracting only a horizontal high frequency component of the video signal;
a horizontal multiplying step of multiplying an output in the horizontal step and an output in the longitudinal detecting step;
a step of deducting an output in the horizontal multiplying step from the video signal;
a vertical step of extracting only a vertical high frequency component of the video signal;
a vertical multiplying step of multiplying an output in the vertical step and an output in the lateral detecting step; and
a step of deducting an output in the vertical multiplying step from the video signal, wherein
the block noise is eliminated according to the block noise level.
According to a forty-fourth aspect, in the thirty-ninth to forty-third aspects,
the program further comprising a step of controlling a picture enhancement level emphasizing an outline of the video signal according to the block noise level detected in the step of detecting as to the longitudinal direction and the step of detecting as to the lateral direction.
According to a forty-fifth aspect, in the thirty-ninth to forth-fourth aspects, the program further comprises a step of specifying the video signal (types or quality thereof, for example) to be inputted in accordance with the block noise level detected in the step of detecting as to longitudinal direction and the step of detecting as to the lateral direction, wherein
in the specifying step, the specification result is onscreen-displayed on a screen in a predetermined format.
A forth-sixth aspect is directed to a recording medium containing a program recorded thereon, to be run in a computer device, for detecting block noise in the vertical or horizontal direction from a digital video signal subjected to lossy encoding on a predetermined image block basis caused by decoding the video signal, the program for realizing an operational environment on the computer device comprising the steps of:
extracting only a vertical or horizontal high frequency component of the video signal;
taking an absolute value of the extracted high frequency component signal;
accumulating/adding the absolute-value-taken high frequency component signal in the horizontal or vertical direction;
again extracting a high frequency component from the accumulated/added high frequency component signal;
accumulating/adding a signal outputted in the step of again extracting the high frequency component on a predetermined N-point basis (N is a positive integer);
detecting the block noise level of the video signal by computing the signal outputted in the step of again extracting the high frequency component in the temporal direction;
determining a maximum value and a position thereof among N-piece accumulated/added values determined by the accumulation/addition; and
masking the detected block noise level at the position of the maximum value, and determining a vertical or horizontal block boundary corresponding to the position.
A forty-seventh aspect is directed to a recording medium containing a program recorded thereon, to be run in a computer device, for controlling a dot clock to be regenerated in a video processing system in which a digital video signal subjected to lossy encoding on a predetermined image block basis is processed, the program for realizing an operational environment on the computer device comprising the steps of:
receiving the video signal, and detecting, with respect to the video signal, a block boundary (where block noise is generated) in the longitudinal direction on a screen; and
changing clock delay in such a manner that the detected block boundary periodically has a single maximum point (peak) with respect to a clock generating device in which the dot clock used for the video processing system is generated based on a horizontal synchronizing pulse.
According to a forty-eighth aspect showing the preferable and concrete technique, in the forty-seventh aspect, the detecting step further comprises the steps of:
extracting only a horizontal high frequency component of the video signal;
taking an absolute value of the extracted high frequency component signal;
accumulating/adding the absolute-value-taken high frequency component signal in the vertical direction;
again extracting a high frequency component from the accumulated/added high frequency component signal; and
accumulating/adding the signal outputted in the step of again extracting the high frequency component on a predetermined N-point basis (N is a positive integer).
As described above, the thirtieth to forty-eighth aspects are directed to a recording medium on which a computer program for executing each function realized by each device in the first to twenty-ninth aspects is recorded. This is for supplying the first to twenty-ninth aspects in the form of software for an existing device.